Most natural populations are affected by seasonal changes in temperature, rainfall, or resource availability. Seasonally fluctuating selection could potentially make a large contribution to maintaining genetic polymorphism in populations. However, previous theory suggests that the conditions for multilocus polymorphism are restrictive. Here, we explore a more general class of models with multilocus seasonally fluctuating selection in diploids. In these models, the multilocus genotype is mapped to fitness in two steps. The first mapping is additive across loci and accounts for the relative contributions of heterozygous and homozygous loci-that is, dominance. The second step uses a nonlinear fitness function to account for the strength of selection and epistasis. Using mathematical analysis and individual-based simulations, we show that stable polymorphism at many loci is possible if currently favored alleles are sufficiently dominant. This general mechanism, which we call "segregation lift," requires seasonal changes in dominance, a phenomenon that may arise naturally in situations with antagonistic pleiotropy and seasonal changes in the relative importance of traits for fitness. Segregation lift works best under diminishing-returns epistasis, is not affected by problems of genetic load, and is robust to differences in parameters across loci and seasons. Under segregation lift, loci can exhibit conspicuous seasonal allele-frequency fluctuations, but often fluctuations may be small and hard to detect. An important direction for future work is to formally test for segregation lift in empirical data and to quantify its contribution to maintaining genetic variation in natural populations.

Apparent competition is an important process influencing many ecological communities. We used predator-prey theory to predict outcomes of ecosystem experiments aimed at mitigating apparent competition by reducing primary prey. Simulations predicted declines in secondary prey following reductions in primary prey because predators consumed more secondary prey until predator numbers responded to reduced prey densities. Losses were exacerbated by a higher carrying capacity of primary prey and a longer lag time of the predator's numerical response, but a gradual reduction in primary prey was less detrimental to the secondary prey. We compared predictions against two field experiments where endangered woodland caribou (Rangifer tarandus caribou) were victims of apparent competition. First, when deer (Odocoileus sp.) declined suddenly following a severe winter, cougar (Puma concolor) declined with a 1-2-year lag, yet in the interim more caribou were killed by cougars, and caribou populations declined by 40%. Second, when moose (Alces alces) were gradually reduced using a management experiment, wolf (Canis lupus) populations declined but did not shift consumption to caribou, and the largest caribou subpopulation stabilized. The observed contrasting outcomes of sudden versus gradual declines in primary prey supported theoretical predictions. Combining theory with field studies clarified how to manage communities to mitigate endangerment caused by apparent competition that affects many taxa.

Action programmes fostering partnerships and bringing together regional and national authorities to promote the care of depressed patients are urgently needed. In 2001 the 'Nuremberg Alliance Against Depression' was initiated as a community-based model project within the large-scale 'German Research Network on Depression and Suicidality' (Kompetenznetz 'Depression, Suizidalität'). The 'Nuremberg Alliance Against Depression' was an action programme, conducted in the city of Nuremberg (500,000 inhabitants) in 2001/2002, addressing four intervention levels (Hegerl et al. Psychol Med 2006;36:1225). Based on the positive results of the Nuremberg project (a significant reduction of suicidal behaviour by more than 20%) 18 international partners representing 16 different European countries established the 'European Alliance Against Depression' (EAAD) in 2004. Based on the four-level approach of the Nuremberg project, all regional partners initiated respective regional intervention programmes addressing depression and suicidality. Evaluation of the activities takes place on regional and international levels. This paper gives a brief overview of the background for and experiences with the EAAD. It describes the components of the programme, provides the rationale for the intervention and outlines the current status of the project. The aim of the paper is to disseminate information about the programme's potential to reduce suicidal behaviour and to provide examples of how European community-based 'best practice' models for improving the care of depressed patients and suicidal persons can be implemented using a bottom-up approach. EAAD is mentioned by the European commission as a best practice example within the Green Paper 'Improving the mental health of the population: Towards a strategy on mental health for the European Union' (European Commission 2005).